The project is designed to: (1) secure replicate measures of physiological, pathological, biochemical and psychological variables on longitudinal study participants at specified intervals; (2) summarize and compare the results of testing in relation to age according to cross-sectional and longitudinal formats; (3) identify characteristics of individual participants which may be related to changes of function over time and to age at death; and, (4) determine whether the data obtained support one or another theory of the mechanisms responsible for age-related functional decrements. Testing Procedures: Psychological tests include especially designed procedures which assess verbal learning and problem-solving abilities as well as standardized tests of intelligence and personality. Physical examinations and medical histories are performed with check lists to insure completeness. Smoking habits, dietary intake, and marital and sexual adjustments are obtained by questionnaire, diary and interview. Both conventional and special procedures are used to assess physiological areas such as kidney function, pulmonary function, neuromuscular function, cardiovascular function, and special senses.